Question

a series is 3, 15, 27,39,.........is 785 a term of this series

Answer 1

Answer:

given : a = 3, d = 12,

to find whether 785 a term ?

aₙ = a + (n - 1) d

let 785 be a term

therefore 785 = 3 + (n - 1) 12

785 = 3 + 12n - 12

785 = 12n - 9

12n = 785 + 9

12n = 794

n = 794/12

n = 66 ²/₁₂

n = 66 ¹/₆

as n is not a whole number, 785 is not a term of the given A.P.

n has to be a whole number in a A.P and G.P